<template>
  <h2>Child子级组件</h2>
  <h3>age:{{age}}</h3>
  <h3>length:{{length}}</h3>
</template>

<script lang='ts'>
import {
  defineComponent, toRef, Ref, computed
} from "vue";
function useGetLength(age:Ref) {
  return computed(() => {
    return age.value.toString().length;
  })
}
export default defineComponent({
  name:'Child',
  props:{
    age:{
      type:Number,
      require:true,
    }
  },
  setup(props) {
    const length = useGetLength(toRef(props,'age'))
    return {
      length
    };
  },
});
</script>
